In signal processing systems in which a number of devices operate on the input data, there arises the need to maintain the relative phases between a number of parallel signal processing channels. Conventional phase shifting circuits operating on the raw data before it enters the devices have been used, but differences within the processing devices are then not compensated.
In the case where the processing devices employ SAWs, the difficulty in the prior art referred to above is compounded because SAW devices depend on temperature, stress on the device, etc., so that there are interchannel differences that must be compensated. In addition to coarse control of the relative phase, vernier control is also required in high accuracy digital applications.